This invention relates generally to surgically implanted shunt systems and related flow control valves. More particularly, this invention relates to shunt systems including one-way flow control valves for controlling the flow of cerebrospinal fluid out of a brain ventricle and preventing back flow of fluid into the brain ventricle.
As is well known in the medical arts, to relieve undesirable accumulation of fluids it is frequently necessary to provide a means for draining a fluid from one part of the human body to another in a controlled manner. This is required, for example, in the treatment of hydrocephalus, an ailment usually afflicting infants or children in which fluids which ought to drain away instead accumulate within the skull and thereby exert extreme pressure and skull deforming forces.
In treating hydrocephalus, cerebrospinal fluid accumulated in the brain ventricles is drained away by a catheter inserted into the ventricle through the skull, and the catheter is connected to a tube which conducts the fluid away from the brain to be reintroduced into the vascular system, as by extending through the patient's jugular vein to the atrium portion of the heart. To control the flow of cerebrospinal fluid and maintain the proper pressure in the brain ventricle, a pump or valve is placed in the conduit between the brain and the heart.
Many such devices have been previously used, but several of these devices have tended to become obstructed by particulate matter entering the drainage system or by the backward diffusion of blood into the system. Further, some prior devices have included moving parts which tended to adhere to other parts of the device and become immobile. When this occurs, the device itself becomes a barrier in the drainage system, and adds to the problem it is intended to solve.
Moreover, manufacturers have been faced with a dilemma regarding the use of metal components in such valves. Some prior devices have included metal components which tended to interfere with X-ray photography and produce radiation scatter ("sunburst effect") on films taken by computerized axial tomography (CAT) scanning equipment, and such X-ray photography and CAT scanning frequently accompanies the use of surgically implanted flow control valves.
It is often desirable to provide an antechamber as a component of a shunt system between the ventricular catheter and the flow control valve. Such placement of an antechamber as a component of the shunt system enables a physician to inject medication into the shunt system at a convenient location for flushing either distally or proximally. It has further been found desirable to provide a needle shield within the antechamber to provide means for detecting the location of the end of a needle inserted into the antechamber, and to further insure that the needle does not pass all the way through the antechamber where medication might be injected directly into the surrounding tissue. Although the benefits of a needle shield are self-evident, several problems have been encountered in prior devices. One problem relates to the unintended obstruction of the free flow of fluid from the ventricular catheter through the antechamber to the flow control valve. The positioning of a needle shield within an antechamber often presents the possibility that the antechamber can itself become occluded or become obstructed, and present a barrier in the drainage system. Another problem presented in prior antechambers is that after initial contact is made between the end of a needle and the needle shield, slight forces exerted on the needle may cause its tip to slide off the needle shield and, unknowingly, pass through the antechamber. This can lead to the injection of medication into the tissue surrounding the antechamber, rather than within the antechamber itself.
Further, in many instances it is believed to be desirable to reduce the size of the various shunt system components as much as possible without interfering with the desirable shunting and/or valving characteristics of the shunt system. With regard to the umbrella-type valve members illustrated in U.S. Pat. No. 4,560,375 (the contents of which are incorporated herein by reference), it has been found that the overall flexible nature of the elastomer materials comprising the flow control member effectively limits the smallest useful size of such members. In particular, during assembly of valves utilizing such umbrella-type members, the central support is pulled through an aperture in the base to position the resilient membrane with respect to one or more fluid flow apertures. As the size of the flow control member is reduced, and therefore the size of its central support, the inherent flexibility of the elastomer central support tends to make proper positioning of the resilient membrane very difficult. This difficulty arises from the fact that the central support undesirably stretches as it is being positioned within the base under most standard assembly procedures.
Accordingly, there has been a continuing need in the medical arts for convenient and effective devices for controlling the flow of fluid from one part of the human body to another, which devices are relatively inexpensive to manufacture and can be constructed substantially of nonmetallic parts which are not subject to adhering to one another and causing a malfunction of the device. Further, such a device is needed which utilizes multiple valve membranes in series for safety and reliability. Additionally a novel flow control member is needed which permits the economical manufacture and assembly of flow control valves on a smaller scale than that previously possible. Moreover, a shunt system is needed which includes an antechamber wherein medication can be injected between the ventricular catheter and the flow control valve, which antechamber provides means for effectively positioning the end of a needle within the injection chamber and yet is of such a construction that the unobstructed flow of fluid through the injection chamber is assured. As will become apparent from the following description, the present invention satisfies these needs and provides other related advantages.